# Definition for a binary tree node.
import collections
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution(object):
    def sortedArrayToBST(self, nums):
        """
        :type nums: List[int]
        :rtype: TreeNode
        """

        if len(nums)==0:
            return None
        length = len(nums)
        mid =  int((0+length)/2)

        root = TreeNode(nums[mid])

        root.left = self.sortedArrayToBST(nums[:mid])
        root.right = self.sortedArrayToBST(nums[mid+1:])
        return root








a= [1,2,3,4]
s = Solution()
m = s.sortedArrayToBST(a)
print(m)
